Question

The coefficient of performance of a refrigerator is $5$ . If the temperarture inside freezer is $-{20}^0$C, the temperature of the surroundings to which it rejects heat is

• A. $21°C$
• B. $31°C$
• C. $41°C$
• D. $11°C$

Answer 1

The correct option is B $31°C$

$5=\frac{heat}{workdone}$
$5=\frac{T\left(fr\right)}{T\left(surr\right)-T\left(fr\right)}$
$5=\frac{253K}{T-253}$
$5T-1265=253$
$5T=1518$
$T=303.6Kor{30.6}^{0}C$
We get, $T={30.6}^{0}C.$